Small terrier and chiwawa pistol/pepper/bb gun

Ok so here is an odd ball topic. I would first like to say I love animals and believe that bad animals are caused by bad owners.

Having said that I own cats that naturally stay outside many times. I live in FL and thier are lease laws with dogs. Well for the morons on my street that does not seem to matter. They leave their dogs outside, unchained. Of course they run around my neighborhood and like to chase my cats. After calling animal control several time and them doing nothing I have decided to take matter into my own hands. Now FL is odd because killing a dog, even by accident runing over, I can get in touble with the law(unless I fear for my safety which trust me I will use as defense as one of them is aggresive and comes into my yard barking and growling at me). So I have been looking at guns becuase mine are way to loud so been checking out .22. I realise the problem with this is I live in city and firing them off is illegal(tho no one lives next to me so worst case I have to worry about a dead dog). So I am looking at alternatives to have the dog get the message to not mess with my cats in my yard.

But yuuichi why not talk to owners? Great idea but retaliation is what I am worried about.

So for a small terrier/chiwawa(the chiwawa seems to be the follower) is there a good CO2 BB gun that can give the dog the business, and what good pepper spray is there?